ABSTRACT
The present study was carried out to evaluate and compare two different designs for restoring unilateral mandibular distal extension [Kennedy class II]. Twenty patients were selected from the Proshtodontic out patient clinic Faculty of Dentistry, Tanta University. Their age ranged from 30-40 years. They had mandibular distal extension opposing natural teeth. All the patients were free from any systemic diseases that might influence the results. Also they had no previous prosthetic appliances. They were subjected to proper scalling, root planning and occlusal adjustment when necessary. The patients were randomly classified into two groups Group A: received RPD containing the distal saddle, Ceka extracoronal attachment, lingual bar and double Acker clasps. While Group B: received RPD containing the distal saddle, RPI clasp, cingulum rest on both canines, lingual bar and double Acker clasps. The following investigations were carried out; periodontal reaction of the abutments [Pocket depth, Gingival index and Probing attachment level], bone changes at abutments and residual alveolar ridge areas using Quantitative digital subtraction radiography and Gray scale levels. The results showed that the mean gingival scores in the Ceka group were higher than the RPI ones as regards the mean pocket depth and the mean attachment level. The mean alveolar bone loss in the Ceka group was high and statistically significant when compared to the RPI one. Based on the previous clinical and radiographical results, it could be concluded that:- The RPI clasp assembly causes less alveolar bone loss at the abutments compared to the Ceka assembly. The RPI clasp causes less resorption rates at the residual alveolar ridge when compared to the Ceka design. The RPI group showed less bone density changes when compared to the Ceka group. It can be concluded that the gingival indices may not be sufficient to reflect the changes of the whole periodontium. While the quantitative digital subtraction radiography enable the numerical statistical analysis between the study groups. Using the Gray scale level to trace the bone density changes is a sensitive alarming methodology pointing out to the sites of future bone loss before it occurs
ABSTRACT
Zirconium oxide has become the subject of dental research in various dental branches. Zirconia ceramics have several advantages over other ceramic materials, due to the transformation toughening mechanisms operating in their microstructure that can give very interesting mechanical properties. The results revealed that the mean value of [flexural, compressive, shear strength, modulus of elasticity and thermal conductivity] were significantly higher in specimens that sintered at 1350 [degree sign] C than that sintered at 1200[degree sign] C